Electron tube apparatus



Feb. 7, 1961 R. 'B. NELSON 2,971,115

ELECTRON TUBE APPARATUS Original Filed June 14, 1955 5 Sheets-Sheet 1INVENTOR Richard 8. Nelson Feb. 7, 1961 R. B. NELSON 2,971,115

ELECTRON TUBE APPARATUS Original Filed June 14, 1955 5 Sheets-Sheet 2:EIE 5 ATTORNEY Feb. 7, 1961 R. B. NELSON 2,971,115

ELECTRON TUBE APPARATUS Original Filed June 14, 1955 5 Sheets-Sheet 3IE'II3 3. 0 w

INVENTOR M Richard B. Nelson ATTORNEY Feb. 7, 1961 R. B. NELSON ,971,

ELECTRON TUBE APPARATUS Original Filed June 14, 1955 5 Sheets-Sheet 4dig INVENTOR Richard 8. Nelson BY W ATTORNEY Feb. 7, 1961 R. B. NELSON2,971,115

' ELECTRON TUBE APPARATUS Original Filed June 14, 1955 5 Sheets-Sheet 580 IN VENTOR Richard B. Nelson BY Map/7M5 ATTORNEY United States PatentELECTRON TUBE APPARATUS Richard B. Nelson, Los Altos, Calif., assignorto Varian Associates, San Carlos, Calif., a corporation of California 8Claims. (Cl. 315-) This invention relates, in general, to electron tubeapparatus and, in particular, to novel electron tube apparatus of thetype employing cavity resonators such as, for example, high powerklystron tubes utilized in systems found in radar, navigation beaconsand linear accelerators, etc. The present invention has been divided outof an earlier filed application for Electron Tube Apparatus, Serial No.515,327, filed June 14, 1955.

In the art of high frequency amplification, for example, that range offrequencies between 2500 and 4000 mc., there has been lacking a pulsedamplifier that would provide high gain, that is, 55 db or over; highpower, that is 1 megawatt or more with an average power of 2 kw., at thesame time combining reliability and long life (1000 hours) with ease ofoperation.

Accordingly, it is the object of this invention to provide a novel highpower, high gain, electron tube apparatus offering ease of operation,long life, and electrical stability.

One feature of this invention is a novel take-apart joint allowing thejoined elements to be separated and then reassembled without thenecessity of cleaning the prior adhesive material from the joint therebypreserving the previously acquired alignment.

Another feature of this invention is a novel cathode button supportwhich prevents microphonics and increases thermal efficiency.

A further feature of this invention is a novel system of stiffenerplates and strengtheners which maintain proper alignment and rigidity ofthe apparatus under adverse shock, vibration and temperature conditionsthereby materially contributing to stable electrical performance.

Other features and advantages of this invention will become apparentfrom a perusal of the specifications taken in connection with theaccompanying drawings wherein,

Fig. l is an elevational view partly in section showing the assembledelectron tube apparatus of this invention,

Fig. 2 is a fragmentary side elevation of the structure of Fig. 1,

Fig. 3 is a cross sectional elevational view of the cathode assemblytaken along line 3-3 of Fig. 2,

Fig. 4 is a fragmentary view of Fig. 3 showing the cathode take-apartjoint,

Fig. 5 is an enlarged fragmentary view of the novel cathode buttonsupport,

Fig. 6 is an enlarged part sectional view taken along line 6-6 of Fig. 2looking in the direction of the ar rows, and

Fig. 7 is a sectional view taken along line 77 of Fig. 2 looking in thedirection of the arrows.

The construction of the novel electron tube apparatus will now bedescribed followed by a description of the operation and function of theapparatus.

Referring now to Fig. l, the novel tube apparatus comprises a cathodestructure 1, resonators 2, 3, 4 and 5 and a collector assembly 6. Signalenergy to be amplified is supplied to the first resonator 2 via aconcentric line input 7 and amplified in successive resonators 3 and 4.The amplified signal is extracted from the output resonator 5 andpropagated to the load through waveguide 8. The cathode is immersed inan oil bath contained within a tank 9 to prevent arc-overs in theexternal cathode region. Surrounding the resonators is an electricalcoil 11 for creating a strong magnetic field to confine the electronbeam in the resonator region.

Referring now to Fig. 3, a source of electrons is supported from andcontained within an evacuated cathode envelope 12. Comprising thecathode envelope are a plurality of tubular segments 13, 14, 15, 16, 17,18, 19, 21 and 22 joined together at their ends. Of these tubularsegments 16, 19 and 22 are of good insulating material as of glass toallow independent operating potentials to be applied to certain portionsof the cathode assembly. Tubular segments 13 and 14 are made ofmaterials having a high magnetic permeability as of steel to provideshielding of the cathode from magnetic fields in the cathode vicinity.The cathode envelope is closed at its lower end by a bottom cup 23 andat its upward end is securely held by pole piece 24.

To allow the cathode assembly to be replaced a novel take-apart jointbetween cathode envelope segments 13 and 14 is provided (see Fig. 4). Atthe joint, proper longitudinal alignment of the lower cathode structureis obtained through the upper horizontal interface. Correct transversealignment of the cathode is obtained through the vertical interface.Interposedl between these two interfaces is an area of mutually opposingsurfaces which are noncontacting, that is, the opposing faces are spacedapart. These surfaces are spaced apart to create a void which destroysthe capillary action tending to draw the adhesive substance 25 from itsapplied region through the horizontal interface and onto the verticalinterface. If the void is not provided adhesive material willcontaminate a greater portion of the interfaces.

When the lower cathode assembly is then to be replaced, the adhesivematerial sticking to the aligning surfaces must be removed. Oftentimesin cleaning the adhesive from these surfaces the previously acquiredalignment is destroyed. The present novel joint design allows thecathode to be removed, worked on and replaced without expendingunnecessary time in cleaning the joint, meanwhile preserving thepreviously acquired proper transverse alignment.

Encircling the cathode envelope at segment 17 and fixedly securedthereto is a novel annular cathode flange 26. The cathode flange is ofheavier construction and serves to strengthen the more fragile cathodeenvelope. Furthermore cathode flange 26 serves as a bumper protector forthe glass insulator 16.

The internal cathode structure is shown in detail in Fig. 3. Containedwithin the cathode envelope 12 is preferably a concave cathode emitter35 having an annular focus ring 36 positioned slightly in front of saidbutton and carried by a tubular focus shield 37 which in turn issupported from the cathode envelope by focus shield support 38. Fixedlysecured to the cathode focusing ring 36 and extending downwardlytherefrom is a novel tubular cathode emitter support 39 (see Fig. 5)having slots running longitudinally thereof thereby creating a pluralityof fingers 41. Also carried by the focus shield 37 is an annular doublepartition heat shield 42 (Fig. 3).

The present novel cathode construction features a cathode emittersurrounded by a plurality of partitions all serving to retain the heatenergy within the cathode emitter region thereby substantiallyincreasing thermal efficiency. The cathode emitter support 39 isparticularly unique in that the longitudinal slots serve to inhibit heatconduction while the finger portions" 41 reflect the'heat' energy backto the cathode emitter. It has been found that certain fingers may becut out to aid in evacuation of the inner cathode regions withoutsubstantially impairing thermal efficiency. A second embodiment of thenovel cathode emitter support 39'has certain fingers bent outwardly ashort distance to substantially a condition of constant diameter forthose portions of the tubular member, leaving a plurality of convergentfingers. This novel design further prevents heat loss by conductionsince fewer fingers make contact with the cathode emitter. In allembodiments the cathode emitter 35 is rigidly secured to theextremitites of certain of the button support fingers.

Heating the cathode emitter 35, a double spiral wound filament 43 issupported upon three support rods, longer heater lead 44, short heaterlead 45 and center support 46. Since center support 46 carries nocurrent it is insulated electrically from the heater filament 43 throughinsulator 47. Extending into the insulator and connecting directly tothe filament, is heater support 48. Providing base supports for shortheater lead 45 and filament center support 46 are two circular plates,heater support flange 49 and getter flange 51 respectively, said flangesbeing rigidly secured to the cathode envelope 12. Long heater lead 44extends downwardly through noncontacting openings in heater supportflange 49 and getter flange 51 and anchors on bottom cup 23. i

Referring now to Figs. 2 and 6, a plurality of reentrant type cavityresonators 2, 3, 4 and 5 are spaced along thick-walled cylindrical drifttubes 52.. Spiraling around the drift tubes is a cooling coil 53 throughwhich is circulated a coolantto carry away heat generated in the drifttube vicinity. Encircling and securely afiixed to the drift tubesubstantially at either end thereof are two magnetic pole pieces,cathode pole piece 24 and anode pole piece 54. A plurality of stiffenerplates 55 likewise encircle the drift tube and are spaced apart in thedrift tube midsection. interconnecting the pole pieces and stiffenerplates are a plurality ofstiifener rods 56 which are rigidly secured tothe stiffener plates as by brazing. It has been found that byutilization of the novel stiffener plates and rods the microphonictendency of such an electron tube apparatus was substantially reduced.Moreover, electrical stability under high ambient temperatures wasgreatly enhanced. Because of the magnetic focusing, not yet fullydescribed, the aforementioned magnetic pole pieces 24 and 54 areconstructed of a material of high magnetic permeability such as, forexample, iron. On the other hand, in the area between the pole piecesthe magnetic field should not be perturbed, thus Where possible partsshould be made of materials possessing no magnetism, for example, thestilfener rods 56 and plates 55 could be constructed of a non-magneticvariety of stainless steel.

In operation electrons are emitted from the cathode focused into a beamby the focusing electrode 36 and accelerated through the drift tube. Thesignal to be amplified is fed into the input cavity 2 where the beam isvelocity modulated. As the modulated beam travels down the drift tube itis further modulated by the intermediate bunching cavities 3 and 4,while within the drift tube the beam is confined in diameter againstforces tending to spread the beam, such as space charge forces, by themagnetic field lines supplied by the focusing coils 11, said lines offlux being parallel to the drift tube in this region. The output cavityextracts electromagnetic energy from the modulated beam and said energyis then coupled out of the output cavity through iris 74 (see Fig. 7)and propagated through waveguide 8- and window 75 to the load. Tuning ofthe tube is obtained by a movable'wall type tuning plunger which ismovable within the resonator by rotation of a worm shaft, not shown,which operates upon actuating rod 66 which in turn cooperatesthroughpinion" 65 "to cause tuner rack support and-attached plunger anddiaphragm to move in and out of the cavity thereby changing the resonantfrequency of-said cavity. I

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended thatallmattercontained in the above description or sho wn in the accompanyingdrawings shall be interpreted as illustrative and not me limiting sense.I p

This application is a division of US. application, Serial No. 515,327,filed June 14, 1955, now U.S. Patent No. 2,944,187.

What is claimed is:

1. In an electron tube apparatus a vacuum tight takeapart jointcomprising two tubular segments of the cathode envelope having a pair ofmutually opposing surfaces and adapted to be sealed together via theintermediary of a sealing material, certain portions of said opposingsurfaces forming a longitudinal aligning interface, certain otherportions of said opposing surfaces at right angles to said longitudinalaligning interface forming a transverse aligning interface, and portionsof said opposing surfaces disposed between said longitudinal and saidtransverse aligning interfaces spaced apart to create a voidtherebetween to prevent contamination of the aligning surfaces bysealing material.

2. In an electron tube apparatus a cathode emitter support comprising atubular support having slots at one end running longitudinally thereinforming a plurality of fingers, and only certain of said fingersconverging inwardly and physically coupled and electrically conductivelyconnected to the cathode emitter thereby rigidly supporting the emitterin a substantially microphonic free manner.

3. In an electron tube apparatus a cathode emitter support comprising atubular support slotted such as to form a plurality of fingers, andcertain of said fingers physically coupled and electrically conductivelyconnected to the cathode emitter, and the cathode emitter supported fromsaid fingers in enveloping relationship whereby the emitter issubstantially contained within said tubular support thereby minimizingthe escape of radiant heat energy and serving to retain the energywithin the vicinity of the cathode emitter thereby increasing theemission efficiency in use.

4. In an electron tube apparatus utilizing theinteraction of a highfrequency electromagnetic field with a pencil-like beam of electronspassable therethr'ough, an elongated rigid tubular vacuum envelopecontaining the beam-field interaction spaces therewithin, strengtheningplate means disposed transversely of and rigidly coupled to saidelongated tubular envelope, and strengthening rod means rigidly coupledto said strengthening plate means andrunning longitudinally of saidrigid'elong'ated envelope toprovide a rigid integral structure therebyminimizing unwanted microphonics and preventing shock and vibrationaldistortions of the electron tube apparatus.

5. In an apparatus as claimed in claim 4 wherein said elongated rigidtubular vacuum envelope comprises a thick-walled tubular segment formingthe drift tube portion of the electron tube apparatus, a' tubularsegment of thinner wall construction than said drift tubesegment forminga cavity resonator portion for containing theelectromagnetic fields ofthe tube apparatus in use, and wherein said strengthening plate meansare carried upon said thick-walled drift tube segments whereby therelatively large mass of the drift tube segments is rigidly supported tothereby prevent unwanted microphonics in vibrational environments.

6. In an apparatus as claimed in claim 5 wherein said strengthening rodsand said strengthening plates are made of a non-magnetic material. 7 p

7. The apparatus according to claim 3 wherein-the cathode emitterincludes a tubular member portionhaving a first and second end portionand being closed at said first end portion by a wall having a concavesurface forming an electron emitting surface of the emitter, saidemitter support fingers having free end portions, and said tubularmember portion of the cathode emitter and said emitter support fingersbeing fixedly physically and electrically connected together at the freeends of said certain emitter support fingers and substantially at thevsecond end of said tubular cathode member for minimizing conduction ofthermal energy from said cathode emitter in use.

8. The apparatus according to claim 7 wherein certain other of saidsupport fingers have their free end portions spaced apart from saidsecond end portion of said tubular cathode emitter member portion.

No references cited.

